An updated version of LDAPAgent with support for the OpenLDAP 2.x client library and various bug fixes is available in the lukeh-OpenLDAP branch of Services/netinfo/servers/lookupd, in Apple's Darwin CVS repository.
lukeh@padl.com

For current versions of Mac OS X, you should use Directory Services to access LDAP servers, as LDAPAgent is no longer supported.
lukeh@padl.com